The objectives of this study were to characterize the distribution of immunoreactive peptide-YY (PYY) in the dog pancreas and to examine whether vagal stimulation can release PYY from the pancreas. Levels of pancreatic polypeptide (PP) were also measured. PYY levels in extracts of the right lobe (0.43 ± 0.03 ng/mg tissue) and head (0.35 ± 0.12 ng/mg tissue) of the pancreas were approximately 10- to 20-fold higher than those in extracts of the stomach (0.03 ± 0.01 ng/mg tissue; P < 0.05) and left lobe of the pancreas (0.02 ± 0.01 ng/mg tissue). However, PYY levels in extracts of the pancreas and stomach were significantly lower than PYY levels in extracts of the colonic mucosa (7.63 ± 0.71 ng/mg tissue). PP levels were significantly (300-fold) higher in pancreatic extracts than in stomach and colonic extracts. Immunoreactive PYY and PP in pancreatic and colonic mucosal extracts coeluted with synthetic PYY and PP standards on HPLC. Electrical vagal stimulation of dogs resulted in a significant (P < 0.05) release of PYY and PP, which was abolished by atropine treatment (2 mg/kg, iv). PYY levels in the pancreatic veins increased more quickly than in the peripheral veins. The integrated levels of PYY in the pancreatic veins [1.63 ± 0.30 ng (0-30 min)/ml] were significantly (P < 0.05) higher than those in peripheral veins [0.86 ± 0.16 ng (0-30 min)/ml], but lower than those in colonic veins [3.14 ± 0.22 ng (0-30 min)/ml]. Our results indicate that PYY is primarily produced in the colon; however, the pancreas contains a measurable amount of PYY, which is mainly distributed in the right lobe and head of the pancreas. In addition, PYY can be released from the pancreas in response to vagal stimulation. These data suggest that pancreatic PYY may participate in the regulation of pancreatic and gastrointestinal functions through endocrine and paracrine actions.
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